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Laser machine shops care a lot about the M 2 parameter of their lasers because the beams will focus to an area that is M 4 times larger than that of a Gaussian beam with the same wavelength and D4σ waist width; in other words, the fluence scales as 1/M 4. The rule of thumb is that M 2 increases as the laser power
[5] [3] As a rule of thumb, the depth should be 1 ⁄ 24 of the span. [5] The width of the ribs is typically 130 mm (5 in) to 150 mm (6 in), and ribs usually have steel rod reinforcements. [5] The distance between ribs is typically 915 mm (3 ft). [3] The height of the ribs and beams should be 1 ⁄ 25 of the span between columns. [3]
The rule of thumb is that M 2 increases as the laser power increases. It is difficult to obtain excellent beam quality and high average power (100 W to kWs) due to thermal lensing in the laser gain medium. The M 2 parameter is determined experimentally as follows: [2]
The American National Standard Z136.1-2007 for Safe Use of Lasers (p. 6) defines the beam diameter as the distance between diametrically opposed points in that cross-section of a beam where the power per unit area is 1/e (0.368) times that of the peak power per unit area.
DIN 1025 is a DIN standard which defines the dimensions, masses and sectional properties of hot rolled I-beams.. The standard is divided in 5 parts: DIN 1025-1: Hot rolled I-sections - Part 1: Narrow flange I-sections, I-serie - Dimensions, masses, sectional properties
ISMB: Indian Standard Medium Weight Beam, ISJB: Indian Standard Junior Beams, ISLB: Indian Standard Light Weight Beams, and ISWB: Indian Standard Wide Flange Beams. Beams are designated as per respective abbreviated reference followed by the depth of section, such as for example ISMB 450 , where 450 is the depth of section in millimetres (mm).
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The beam of many monohull vessels can be calculated using the following formula: = + Where LOA is Length OverAll and all lengths are in feet. Some examples: For a standard 27 ft (8.2 m) yacht: the cube root of 27 is 3, 3 squared is 9 plus 1 = 10. The beam of many 27 ft monohulls is 10 ft (3.05 m).